Britain's FTSE loses ground as Glencore and Morrison fall

* FTSE down 0.8 pct

* Weak Chinese data weighs on mining stocks

* Morrison knocked by downbeat HSBC broker note

* ARM boosted by positive Barron's piece on Apple (NasdaqGS: AAPL - news)

By Sudip Kar-Gupta

LONDON, Sept 14 (Reuters) - Britain's top share index fell on Monday, with miner Glencore (Xetra: A1JAGV - news) and supermarket group Morrison underperforming, as weak Chinese data and the possibility of a U.S (Other OTC: UBGXF - news) . rate rise weighed on markets.

The blue-chip FTSE 100 index had initially risen but then lost ground to stand 0.8 percent lower at 6,071.26 points as caution crept in before this week's U.S. Federal Reserve meeting. The FTSE is down 8 percent since the start of 2015.

A Reuters poll on Friday showed a small majority still expect a Fed hike on Thursday, although other markets-based models suggest policy tightening will be delayed.

A U.S rate hike could put pressure on the Bank of England to follow suit, and higher interest rates often hurt stock markets by boosting the appeal of bonds and cash, which have become ultra-low yielding.

"Sentiment is a bit on the cautious side. I'd definitely be a seller of rallies at the moment," said Beaufort Securities sales trader Basil Petrides.

Weak economic data from China also weighed on miners , since China is the world's biggest metals consumer, and mining company Glencore was further dented by a price target cut from Jefferies.

Chinese stocks fell on Monday after data which suggested that China's economic growth was running below the 2015 target level of about 7 percent.

Morrison also retreated 4.1 percent after HSBC cut its profit forecasts on the supermarket group.

However, technology group ARM climbed 1.6 percent. Traders said ARM was benefiting from an upbeat article by Barron's on Apple, which uses ARM designs in its products.

"We remain buyers of ARM," said Aviate Global founding partner Gary Paulin.

Nevertheless, uncertainty over the Fed's meeting meant any attempts by the FTSE to gain ground could be short-lived, said equity dealers.

"Understandably, as we draw towards Thursday's long anticipated Fed meeting, the willingness of traders to hold a position throughout the whole week is going to be lower," said IG (LSE: IGG.L - news) market analyst Joshua Mahoney.

(Additional reporting by Kit Rees; Editing by Catherine Evans/Ruth Pitchford)